1. Field of the Invention
The present invention relates to a fluid delivery system for dispensing precisely metered quantities of a fluid, and more particularly, relates to a fluid delivery system incorporating a diaphragm pump for effectuation of the precise control over the dispensing of a metered quantity of the fluid through the formation of a fluid flow-occluding air bubble at the point of discharge inhibiting the formation of droplets tending to adversely influence the accuracy of the system. The invention further relates to a method for delivering and dispensing precisely metered quantities of a fluid through the utilization of the system pursuant to the invention.
For the delivery and the dispensing of precisely metered quantities of fluids; for instance, such as reagents which are employed in chemical reactions, fluids for instrumentation devices and methods carrier fluids and the like, it is frequently necessary that the quantities of the fluid which are delivered by the dispensing system are dispensed or dosed in accurate measures when conveyed from a supply of the fluid to a dispensing nozzle, which may be a component of a probe. The degree of dispensing accuracy which is frequently necessary in obtaining the required metered quantity or dosage of the fluid, for example, to an accuracy of within a single droplet of the fluid, not only depends upon the fluid advancing or pumping action of the fluid delivery system, but also upon the tip geometry and material of the dispensing nozzle or probe, the surface tension between the fluid and the therewith contacting material of the dispensing nozzle, the viscosity of the fluid, the flow velocity of the fluid, and upon occasion, the type of reagents from which the fluid is constituted.
2. Discussion of the Prior Art
Although numerous fluid delivery methods and systems are currently known in the technology which relates to the dispensing of extremely precisely metered quantities of various types of fluids, none of these prior art are adapted to provide the necessary degree of precision or dosing accuracy in the dispensing of the specific fluids, for example such as reagents employed in chemical sampling or reactions, or instrumentation fluids, which must be dispensed and/or added to other ingredients to thereby eliminate any kind of error in calibrating the dispensed volume of the fluid.
Thus, Fritsch U.S. Pat. No. 4,430,048 discloses a diaphragm pump in which a flexible diaphragm separates the pump interior into a fluid delivery chamber and a working chamber, and wherein predetermined quantities of a fluid are adapted to be aspirated into and discharged from the delivery chamber in response to alternating pressures being imparted to the working chamber. The alternating or reversing changes in pressure acting on the working chamber will enable the fluid to be dispensed from the delivery chamber in response to the displacement of its diaphragm through a suitable outlet having a non-return valve therein. Although the diaphragm pump and the fluid delivery system which is provided thereby, as described in this publication, facilitates the dispensing or dosing of substantially uniform quantities of a fluid, the system described therein is not adapted to allow for the extremely precise metering of fluids through the formation of an air bubble at the discharge of the system, which will inhibit the formation of fluid droplets at the discharge end of the system tending to adversely affect the accuracy in the dispensing or metered dosing of the fluid.
Hetz U.S. Pat. No. 3,767,326 discloses a control system for regulating the volume of a fluid which is adapted to be dispensed through the reciprocatory action of a diaphragm pump. However, this known system is designed to primarily facilitate the varying of a quantity of fluid being dispensed therefrom during each cycle of operation, in response to the operation of a bypass valve which is actuated by a control circuit. There is no disclosure of any system incorporating a diaphragm pump and a method of utilization thereof to form an occluding air bubble at the discharge end which will facilitate the dispensing of precisely metered or dosed quantities of a fluid at a degree of delivery accuracy required for the most demanding and delicate chemical reactions, and which would inhibit the formation of any residual fluid droplets at the discharge tending to adversely influence the accuracy of dispensed quantities of fluid.
Surre U.S. Pat. No. 2,662,478 discloses a diaphragm pump and compressor arrangement, through which metered quantities of a fluid may be aspirated and then dispensed responsive to the reciprocating action of a diaphragm in a pump subjected to alternating pressure and vacuum being applied to the working chamber of the diaphragm pump. Although this patent describes the basic principle of dispensing a fluid through the intermediary of a diaphragm pump, there is no disclosure of a system providing for the necessary accuracy in dispensing metered quantities of a fluid through the formation of an occluding air bubble at the discharge of the system.
Schmechtig U.S. Pat. No. 4,269,906 describes a pump device in which pulsating pressures in the form of pressure waves are applied to a membrane, causing the membrane to be displaced from the outlet of a conduit and to facilitate the filling of a pump chamber with a certain quantity of fluid and thereafter dispensed from the device by a reversal of pressure. As in the other publications, although this pump device employs the basic principle of a diaphragm pump, there is no utilization nor disclosure of a system allowing for the precision metering or dosed delivery of quantities of a fluid with the formation of an occluding air bubble which will prevent the flow of any residual fluid droplets causing the minutest deviation from the desired dispensed quantity tending to adversely affect the accuracy of the system.
Other diaphragm pumps and systems for dispensing predetermined quantities of fluids or the like are, respectively, disclosed in Kiffer, et al. U.S. Pat. Nos. 2,871,789; Harper 2,308,974; Telford, et al. 3,269,318; Kitsnik 4,439,112; Finger 3,692,433; Di Vette 2,954,738; Bruggeman 3,930,756; Ruth 3,318,324; and Beer 3,556,684, however; none of which provide for the desired or necessary degree of accuracy in dispensing dosages of fluids of the type considered herein.